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Zenith - Calibre 135, an obsession with precision

Zenith Calibre 135, an obsession with precision

Zenith turns the spotlight on its Caliber 135 and his 100-years-old creator watchmaker.

Press release

Zenith turns the spotlight on one of its most amazing movements epitomising an almost obsessive quest for precision, in a presentation symbolically timed to coincide with the 100th birthday of watchmaker Ephrem Jobin in late November 2009, the brains and the hands behind this multiple award-winning mechanism.


Like all Zenith movements, the Calibre 135 stemmed from the company's determination to create ever more accurate and reliable movements – a tradition cultivated since its founding in 1865, illustrated early on by its remarkably accurate pocket-watches, and accentuated by the emergence of wristwatches.

Introduced in 1948 at the height of the fiercely-fought race for precision between various watchmakers, the Calibre 135 comprised several innovative and sophisticated technical features that enabled it to win numerous prestigious Neuchâtel Observatory chronometry prizes, including five years in a row from 1950-1954 – a record in itself. Its total tally of such recognitions comprised around 200 individual honours, two-thirds of which were first prizes, as well as five for series-honours.



Successful research

Ephrem Jobin, born in 1909 and doubtless the world's oldest living watchmaker, played a variety of roles in the development of Zenith at this strategic time. During the period he spent at Zenith between 1939 and 1954, he was responsible for developing three complete calibres, including the legendary Calibre 135.

He quickly grasped the importance of reorganising manufacturing procedures based on a truly global vision of production. When commissioned in 1946 to invent “a 30 mm calibre” capable of meeting the norms of the Neuchâtel Observatory competition, he set about conceiving and developing it according to a set of standards designed to enable it to achieve the best possible chronometric performances. He single-handedly supervised the entire project.


Ephrem Jobin's recipe for success with the Calibre 135 included using a large barrel to increase power reserve, as well as an oversized balance which, as part of the regulating organ, plays a crucial role in enhancing precision. This approach called for a complete rethinking of the movement design, including offsetting the minute wheel from the central axis so as to provide space for the enlarged balance. The observatory competition version of this legendary movement (Calibre 135.0) was equipped with a Breguet overcoil balance-spring, as well as a single or double arrow-shaped index or regulator ensuring balanced friction and enabling optimal adjustment.

Moreover, in addition to its outstanding chronometric feats, Calibre 135 was also adapted to produce commercialised versions, all of them chronometer-certified and sold with a rating certificate. They were equipped with an off-centred disc regulator and adorned with Côtes de Genève.

An exclusive asset

The chronometer-worthy precision of Calibre 135 entailed a naturally limited production volume reserved exclusively for high-end watches. 11,000 of these movements were produced, meaning that watches housing this calibre remain a much-coveted item among connoisseurs and collectors.

The specialised press described it at the time as “one of the best wristwatch movement in watchmaking history” – a title it undoubtedly still deserves thanks to its superlative performances and surprising modern construction. This refined aesthetic appeal, accentuated by the classic design and the meticulous finishing of this calibre, vividly evokes the pure, restrained classicism of Zenith watches.

This historical retrospective tribute to Calibre 135 thereby honours an exceptional example of horological know-how, vividly embodied in the person of an archetypal master-watchmaker and distinguished centenarian, Ephrem Jobin.

Zenith has indeed decided to commemorate this jubilee by issuing a special 100-piece limited-edition watch in his honour and presenting him with the N° 100 model in a nod to his milestone birthday. It is powered by a self-winding COSC-certified Elite 689 movement having notably benefited from the technical progress made during Mr. Jobin's time at Zenith.

The 18-carat rose gold case with sapphire crystals on either side frames an understated, elegant brown sunray dial graced by 18-carat rose gold faceted hands and hand-mounted applied hour-markers. Teamed with a hand-crafted brown crocodile leather strap lined with silky Alvazel calfskin and fitted with an 18-carat rose gold pin buckle, this handsome model eloquently conveys Zenith's gratitude to Mr. Jobin for his major contribution to the history and development of the brand.


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